Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-01-12
2001-04-24
Nguyen, Chanh (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
Reexamination Certificate
active
06222511
ABSTRACT:
BACKGROUND AND BRIEF DESCRIPTION OF THE INVENTION
Creation of pixel-by-pixel gray scale in bistable AC plasma (ACP) displays and DC plasma displays modified to provide bistability has been both studied and demonstrated over the last 20 years. Moreover, full color plasma displays employ pixel-by-pixel gray scale within each color channel. Although the concept has been demonstrated several times, it has been difficult to implement as a product because adequate drive systems were not able to avoid flicker and operate with real time non-interlaced digitized video sources such as VGA.
An early development model, when operated at 30 Hz update and with sequential pixel row scan, has especially noticeable flicker with still frame video and computer generated images. Most prior art gray scale plasma display demonstrations are either not capable of video rate update, or are specifically for broadcast video. In the first case, flicker may be avoided at the expense of not having real time video capability. In the second case, the operation with continuously changing video images tends to mask flicker. In any case, 30 Hz update operation on the ACP display does not sufficiently avoid flicker in static images, although it has been tolerated as an NTSC standard for CRTs. IBM's recently introduced 8514 and 8515 VGA monitors are based on a frame rate of 43.5 Hz for flickerless interlaced operation (Reference Computer Technology 30 view, August 1990, Flicker Free VGA Can Increase User's Productivity). This invention uses 46 Hz (or greater) interlaced update of the display in addition to nonsequential row scan to avoid flicker.
The bistable ACP display is currently produced by several organizations in Europe, Japan and the U.S., each organization making its own versions/configurations of the basic ACP technology. The basic technology incorporates neon gas mixtures as the display medium in the cavity where the matrix imposes pixel-by-pixel control voltages. The matrix may be located on one substrate or on two opposing substrates.
The neon gas mixtures used in ACP displays has certain physical response times which must be accommodated by all electronic drive systems:
1) The neon gas ion mobility is such that 5 microseconds must be allowed after each gas discharge for the ions to be redistributed for bistability in the cell.
2) The erase phenomenon whereby a partial discharge is invoked requires at least 3.5 microseconds duration at discharge cell zero potential.
ACP displays generally have interlaced electrodes which form the X-axis and Y-axis matrix lines: every other electrode is brought out to the edges of the panel so that there is a set of even connections (0, 2, 4, 6 . . .) and odd connections (1, 3, 5, 7 . . .) at the top and bottom respectively, and at the left and right sides, respectively. This electrode connection implementation has been employed to reduce the resolution requirements for drive system interconnect.
VGA BACKGROUND
VGA has become an industry standard de facto. The invention is intended to allow operation with the output from one of the color channels available from VGA sources, typically the Green channel. VGA is the dominant graphics format by far, accounting for 65-75% of all the retail color market and nearly 50% of all monitors (Reference The Marketplace Votes On VGA, Information Display 9/90, pp. 10, 11). VGA requires an analog monitor; that is, each of its R, G and B outputs is 1 volt peak-to-peak analog data. Its horizontal and vertical sync signals, however, are in digital TTL form. Note that the analog data signals for R, G and B are created from digital data which is converted to analog.
Although VGA is a color standard, it is also quite accepted as a monochrome configuration. The standard screen format is 480 pixel rows and 640 column rows. An extended format can either be 600×800 or 768×1024. VGA offers greater clarity than EGA or CGA; it is able to display 256 simultaneous colors from a palette of more than 262,000, and also features high resolution 8×16 text cells. Relative to monochrome applications, up to 64 levels of gray scale are provided per single channel. There are many suppliers of both VGA boards and/or circuits to drive VGA monitors. For example, Western Digital Imaging supplies chip sets for the Paradise VGA card. Many publications over the last 3 years have presented information about VGA, including these examples: VGA Teaches PC/AT Table Manners, MINI-MICRO SYSTEMS, May 1988, pp. 87-98; Enhanced EGA and VGA Boards, BYTE, March 1988, pp. 102-112; Enhanced VGA Boards Pose Compatibility Problems, EDN, Jun. 29, 1989, pp. 8-15; High Resolution Monitors Emerge to Meet Advanced Graphics Needs, Computer Technology Review, Spring 1990, pp. 95-99; and Multisynchronous Monitors: Paying for Flexibility, Information Display 5/90, pp. 17-19.
The standard horizontal frequency for 480×640 VGA is 31.5 kHz. There are actually two VGA pixel frequencies (Reference for example Western Digital's VGA Clock chip, part number WD90C60, data sheet number 79-000512); 25 MHz for graphics mode and 28 MHz for text mode. VGA chip sets and/or PC boards provide the necessary outputs to analog monitors, but many VGA compatible monitors also have multisyncing capabilities which allow a range of frequencies and images to be displayed.
PRIOR ART BACKGROUND
One comprehensive reference for plasma display technology is Topics in Applied Physics, Volume 40—Display Devices, published by Spring-Verlag, J. I. Pankove Editor, 1980. Grayscale operation in plasma displays is discussed in Section 3.8.3 therein, including a SID presentation by engineers from GTE who patented their disclosure of AC Plasma Panel TV Display with 64 Discrete Intensity Levels.
Another reference regarding the drive system for plasma displays is contained in Display Driver Handbook, Driving High Voltage and Flat-Panel Displays, Texas Instruments, 1983, pp. 2-15 through 2-31.
Gray scale driving in plasma displays has also been reported for color plasma displays in Japan: for examples, A Pulse Discharge Panel Display for Producing a Color TV Picture with High Luminance and Luminance Efficacy, NHK authors, IEEE Transactions on Electron Devices, Vol. ED-29, No. Jun. 6, 1982; and Color TV Display with AC-PDP, NHK authors, pp. 514 & 515, Japan Display, 1983.
Thomson CSF of France is advertising 8 level gray scale AC plasma displays, but has not disclosed their approach. Reference AC Plasma Display Panels, Product Selection Guide, Thomson Tubes Electroniques, TTE 15G GP, May 1989.
Toshiba and Panasonic have been offering some plasma display panels with up to 16 levels of gray scale which are designed specifically for personal laptop computer applications. It is understood that they are not capable of full video rate operation.
Fujitsu has just begun offering an AC plasma display with 16 levels of gray scale and VGA compatibility. Reference Electronic Engineering Times, Nov. 12, 1990, page 100. Fujitsu is marketing the display in coordination with a Western Digital VGA controller which apparently buffers the display from real-time analog video that normally would be the output from VGA sources.
Development of AC plasma displays with the matrix located on one substrate is basically represented in A Planar Single-Substrate AC Plasma Display with Capacitive Vias, George W. Dick, Proceedings of the SID, Vol. 20/5, 1979; and Characteristics of Surface-Discharge Color AC Plasma Display Panels, Fujitsu authors, pp. 164 & 165, SID 1981 Digest; and Plasma Display Technologies for A Flat-Panel Color Television, NHK author, Japan Display 1986, pp. 490 through 493.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a drive system for ACP panels on which real time video and computer graphics, both with pixel-by-pixel gray scale are displayed. It is especially an object to provide a system which avoids flicker and allows display of real time non-interlaced digitized video such as VGA in addition to standard interlaced “broadcast” video such as NTSC.
It is additionally an object of t
Stalker Michael B.
Stoller Ray A.
Marshall & Melhorn
Nguyen Chanh
Photonics Systems, Inc.
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